Office environments are usually occupied with a writing board such as a chalk or dry erase board and a projector screen. Businesses are often changing their facilities to accommodate changes in personal and business needs. Often rooms are redesigned to provide conference rooms which were once personal office space. Conference rooms previously contained both a writing board and a projection screen. It is desirable to provide a single article which can meet the need for both the writing surface and projection screen.
Dry erase boards have been used as a writing surface for years because of their convenience and versatility. The boards provide a means for expression which eliminates the mess and trouble of a chalk board. Known boards however are not useful as projection surfaces because of the glare associated with the surface of the dry erase board. If the ordinary dry erase board was used as the projection surface the glare and reflection of the projection bulb leads to eye strain and fatigue to the viewers. Furthermore, these boards generally do not have enough brightness and contrast, particularly under bright ambient light conditions.
It is desirable to have a multi functional article which acts effectively as a dry erase board and a projection screen that can projects image with high brightness, high contrast, and wide viewing angle.
U.S. Pat. No. 5,200,853 (Berkman) discloses a durable multipurpose screening board based on melamine, which comprises an upper section comprising at least two superposed layers of transparent overlay sheets, each of the sheets weighing between 2 and 120 grams per square meter and having been soaked in a solution or melt of a polymeric resin material to subsequently form an intermediate solid plastic layer, the upper surface of the upper sheet being roughened by a plurality of closely-spaced complementary depressions of the depth between 0.01 mm and 0.2 mm, the core section comprising a paper sheet weighing between 60 and 140 grams per square meter and having soaked in a solution or melt of a polymeric resin material to subsequently form an intermediate solid plastic layer. The disclosed screen has low optical gain similar to a white board. It is not high enough to project high contrast, high brightness image under bright ambient light.
U.S. Pat. No. 5,361,164 (Steliga) discloses a projection markerboard having a bi-directional lenticular embossed surface. The light reflecting writing surface is preferably made of a thin film of fluoropolymer, such as a modified copolymer of ethylene and tetrafluoroethylene. The disclosed screen has low optical gain similar to that of a typical white board. It is not high enough to project a high contrast, high brightness image under a bright ambient light.
U.S. Pat. No. 6,476,965 (He et al.) discloses an article useful as a dry erasable substrate and projection screen comprising a top layer which is dry erasable and has a 60° gloss of less than about 60. The disclosed screen has low optical gain similar to a white board. It is not high enough to project high contrast, high brightness image under a bright ambient light.
Display devices generally display information to a viewer. The performance of a display is described in terms of various characteristics of the display. One such characteristic is the ability of the display to absorb ambient light originated from various sources of light such as a light bulb in a room or on a street or the sun. Generally, ambient light that is incident on a display and not absorbed by the display is superimposed on the displayed information resulting in reduced image contrast. The reduced contrast due to ambient light is generally referred to as washout. Washout is especially a concern in applications where the ambient light is very bright. For example, in a room where a dry erase board and a screen is used where ceiling lights and window light are strong, washout of a projected image is not solved by the previously disclosed dual function boards cited above.
Another characteristic of a display is the viewing angle. It is generally desirable that the displayed information be easily viewable over a predetermined range of viewing angles along the horizontal and vertical directions. As one display characteristic is improved, one or more other display characteristics often degrade. As a result, certain tradeoffs are made in a display device in order to best meet the performance criteria for a given display application. Thus, there remains a need for a dry erase board that is able to project image with high brightness, high contrast and wide viewing angle under strong or bright ambient light conditions.